The present invention relates to the field of voice over asynchronous transfer mode (ATM) and specifically to voice over ATM applications that terminate trunk signaling.
Asynchronous transfer mode, commonly abbreviated as ATM, is a connection-oriented, cell based transport service designed to carry a wide variety applications including voice and video images as well as binary computer data over a single distributed switched network. ATM is well suited for the synchronized real time data traffic required by many multimedia applications. The ATM physical layer can take many forms including optical fiber, high speed copper or high speed co-axial wire. Virtually any physical medium can be used which supports a data rate higher than T1 (1.5 Mbps).
Since ATM is fundamentally a connection oriented technology, a connection must be established between sending and receiving nodes prior to data being transferred. This is in contrast to connectionless standards such as Ethernet or Frame relay where nodes send data based on the address of the data packet. A second aspect of ATM, as contrasted with other switching technologies, is that ATM is a cell based design. Typically, an ATM network consists of fixed length cells of 53 bytes. The cell is comprised of a five byte header and a 48 byte payload. A cell contains the image, video and voice transmission data. Coupled with the typical transmission speed of 155 Mbps per second and 622 Mbps provides the ability to build high performance switching system for public and private networks.
In an ATM network, an end-system requests a connection to another end point by transmitting a signal across the user network interface (UNI) to the network. This request is passed to a signaling entity within the network which passes it across the network to a destination. If the destination agrees to form a connection a virtual circuit is setup across the ATM network between two end systems. Mapping is defined between the virtual path identifier (VPI)/virtual circuit identifier (VCI) on both ends of the UNI and between the appropriate input link and corresponding output link of all intermediate switches.
The ATM adaptation layer (AAL) provides the foundation which gives ATM the ability to be service independent, in that ATM is not restricted or limited to a specific traffic type. Within the AAL there are different types of layers designed specifically for different types of traffic. For example, AAL1 handles encoded voice traffic, video and other similar types of data structures. In general, these AALs are defined as being specified by the services they support which, in turn, are based upon three basic transmission characteristics: the time relation between the source and the destination, the bit rate (constant, available, or variable), and the connection mode (connection oriented or connectionless oriented). These AAL services, are further classified into four classes defined by the international telecommunications union (ITU). Into these classes, the different type of network services fit.
As more video and voice applications such as imaging and multimedia are being used in a variety of settings the need for multiple high speed technologies will continue to increase. Currently there is a growing demand for voice and video over ATMs in areas such as tele-medicine, video distribution and distance learning. One feature that would help bridge the gap between ATM networks and such applications is the ability to dynamically allocate an ATM connection or xe2x80x9ctrunkxe2x80x9d on demand. The problem with dynamic trunking, however, is that requires specific and proprietary implementations on both ends of the connection. This reliance on proprietary implementations makes dynamic trunking either a difficult or impossible function to implement in most cases.
Another problem associated with dynamic trunk allocation is that the call exchange hardware and connections are often static or dedicated to particular and specific destinations. The use of dedicated connections limits allocation in the areas where traffic needs exists by reducing the number of exchange configurations in the network. In order to accommodate other destinations new hardware must be added to the system or the existing hardware must be re-engineered thereby increasing the costs and complexity of the network. A way of utilizing the same switching hardware for use towards destinations where traffic increases would be advantageous.
The present invention provides a mechanism for dynamically allocating ATM connections between exchanges that reduces the hardware and maintenance costs of a network by optimizing the use of bandwidth capacity available for carrying voice data between a circuit switching platform and an interworking unit. The invention provides a means of pooling all devices in a node and making them available to traffic in any destination. In one embodiment, device pooling is accomplished in groups of devices forming so called xe2x80x9ctrunksxe2x80x9d so that an individual device itself is not selected although the trunk handling the device is.
According to one embodiment, disclosed is a communications system for dynamically allocating asynchronous transfer mode (ATM) connections between exchanges. The system includes a transfer exchange controller coupled to a first slave exchange with a signaling link extending from the master exchange controller to the slave exchange. The master exchange controller is configured to establish a signal path to the slave exchange through one or more interworking units (IWUs) coupled to each one via an ATM connection. A control link couples the master exchange to a first IWU and a physical connection is established with the first connection IWU providing a signal pathway to the ATM connection. A second IWU at the far end of the ATM connection is likewise physically linked to the slave exchange. Once the physical connections between the IWUs are setup, they can be released and allocated as needed to accommodate traffic needs of the network. The slave exchanges can employ standard ISUP signaling protocols while communications with the IWUs can employ circuit emulation according to ATM adaptation layer 1 (AAL1).
According to another embodiment, disclosed is a method of dynamically allocating ATM connections between exchanges in a signaling network. The method comprises the steps of determining the traffic needs of the network and signaling a slave exchange to determine the capacity to handle the traffic. Next, an ATM connection is established with as many of the slave call exchange units as necessary to accommodate the traffic needs of the network. Standard ISUP signaling protocols can be used for signaling the slave call exchanges. A physical connection with an IWU is established between a master exchange in the network. Next, an ATM connection is established with other IWUs in the network and an IWU at the far end of the connection is physically connected to the slave exchange.